I will do it, too. But I will not do it the way he did.
Docult's creation of the Jumbor following Dunstan's betrayal and disappearance is very clearly derivative. But he doesn't ask his creations to fight one another. He doesn't carve their souls into little pieces. He gives them the joys of humanity. He doesn't fucking mess with the fabric of reality.
At least, he doesn't do so intentionally. He's so deep in his idea that he is inherently better than Dunstan, his spite hides the imperfections in the reality he lives in. The fabric of his realities is intact, sure... but it's so, so fragile. So thin. While Dunstan's creations must be terribly strong to claw their way through the little holes Dunstan left behind, it's like wet paper for Something Else to slip, unnoticed, into the world of the Jumbor.
By tearing away so much of humanity, not just allowing, but enabling Genber to smash the ideas of spirituality and myth and art, he's affected the entire world. He's given space to the things that slowly scrape away at the fabric, that make it thinner and thinner and thinner until it can be seen through.
But Docult doesn't see it. He is tunnel-visioned to his creation. To improving, to expanding. It isn't until he becomes Drill that he starts to let his tunnel expand. That Trickery comes around and forces himself into his awareness. That he actually starts to investigate the existence of Shear. That Vise starts trying to push him to see what he's seen. To accept it.
But to accept it... it means he's no better than the man who chose to protect some criminal guinea pig over the one he claimed to love. Maybe that's part of why he gets lax. Why he starts to let his guard down with regards to his ex. He thinks MAYBE he understands.
He realizes just how fucking wrong he is when he's clinging, desperately, to Shear's unconscious body. Someone he wanted to protect. There is no forgiving Dunstan. The man's madness has only grown.